The Red Bulls’ Supporters Shield dream of having the best regular season record in the league died last night, killed and buried six feet under their own stadium by Sporting KC.

The Red Bulls didn’t allow another early goal in Wednesday night’s first-place clash, but they doubled down and coughed up two on set pieces. Those two goals may prove the costliest scores the Red Bulls will surrender all season as they were harried, harassed and eventually humbled in a 2-0 defeat. It was the Red Bulls’ first home loss, leaving them five points behind in the East.

“[We had] Poor marking on a few set plays in the [beginning], too many lost 50-50s, too many unforced errors, no rhythm in our attacking game,” coach Hans Backe said. “We created a decent number of chances, but couldn’t really hurt them. They were the better team tonight.

“I’m surprised. It’s a big game, we were fighting for No. 1 and you want to win, but they are No. 1. Everyone is disappointed.’’

The Red Bulls (14-8-7, 49 points) had cut Sporting KC’s lead from 11 points to two, but fell in before a season-low crowd of 10,286.

“Overall, they played better,” Thierry Henry said. “Let’s not hide behind anything. They deserve to be first, and they are.

“We created chances, [but] we didn’t score. I said so many times that you’re not going to be able to come back sometimes in a game like that, and that happened. KC were better than us, way better. They attacked the game better than us, and we found ourselves down 2-0 after 20 minutes.’’

Goals by C.J. Sapong and Kei Kamara left the Red Bulls trailing 2-0 after 19 minutes, and now they find themselves five points adrift of Sporting KC with just five games left, and in third place, one point behind a hot Chicago Fire team that holds a game in hand.

Teemu Tainio was whistled for a soft foul on Graham Zusi outside the box, and the MLS assist leader hit his free-kick off the crossbar. The rebound fell to Matt Besler, who tapped it to Sapong for an easy 12th-minute goal, the MLS-worst 11th the Red Bulls allowed in the first 15 minutes of games.

Seven minutes later, Kamara beat Wilman Conde badly on a Zusi corner, getting open for an all-too-easy header and a 2-0 lead. Sporting KC — without a Designated Player and using a fraction of the Red Bulls’ $15 million, three Designated Player payroll — were more athletic and physical, even without Teal Bunbury. Kamara gave Conde fits and Sporting KC were first to seemingly every 50-50.

“We lost the game ourselves,’’ Tim Cahill said. “They’re a good team. We definitely should have competed a lot better.’’